History, literature & psychology
If you know the subject - maybe even have a passion for it...
A good journalist can write about anything, they say. It's only partially true. If you know the subject - maybe even have a passion for it - you can easier ask interesting questions, identify exciting angles, track down the the right sources. History, literature and psychology are areas I've always dealt with and even studied academically, so stories circling in some way around those subjects is something I happily write. Probably with a better outcome too, than if the subject was, let's say football...